In the forming of concrete foundations, concrete walls and columns, an assemblage of panels are connected together in various orientations. The panels are usually three to four feet wide and eight feet high or other suitable dimensions as required by the particular application. Although some contractors still use wooden forms, the more progressive ones use form panels of aluminum or other lightweight metal, whereby the weight is such that a single workman may lift a panel without the assistance of a crane and carry the panel into place to form a wall or to remove it from the green concrete wall after pouring.
Form panels are generally used by the contractor for three types of operations: wall forming, free standing column forming, and in-fill column forming. The wall forming operation is typical foundation or concrete wall work, the free standing column is the type ordinarily employed in reinforced concrete multi-story buildings and the in-fill column is often encountered in combination column and concrete or cinder block wall construction, wherein reinforced concrete columns are interspersed along a concrete block wall at intervals for structural integrity and resistance of the structure to catastrophic failure, as in earthquake prone areas. Typically, a form manufacturer, such as the assignee herein, has had to offer three types of forms to the contractor for each of the above three types of applications, because each form has generally not been adaptable to multipurpose use.
The present invention comprises a form panel intended for multipurpose use, which may be employed in all three applications. The present form offers a significant improvement over its predecessor, the form panel which is described in U.S. Pat. No. 3,899,155, commonly owned with the present application. The prior form panel was constructed of a frame of side rails and top and bottom rails of extruded angle form aluminum alloy arranged about a face sheet of either aluminum alloy or plywood, depending upon the particular needs of the contractor.
A particular problem in the art has been to construct a form which sufficiently resists deflection upon substantial loading or, in the worst case, to prevent blow out or rupture of the forms between adjacent side rails. The goal of both the manufacturer and the contractor is to produce what is termed an L/360 surface, or a smooth, straight, deflection free surface for the finished concrete wall or column. Excessive deflection of the forms under load produces unacceptable results. The problem was particularly apparent in forming columns wherein the weight of the overlying concrete in the column produced tremendous spreading force at the bottom of the forms.
To resist against deflection or catastrophic failure, the concrete form panels disclosed in U.S. Pat. No. 3,899,155, featured cross stiffener members formed of extruded aluminum in a hat section, wherein the hat section extrusions were welded at opposite ends to the side rails and riveted along their length to the face sheet. This form produces highly acceptable results, but such forms were not felt to offer sufficient rigidity when used in column forming operations and were not usable for making in-fill columns.
The present invention is particularly designed as a multipurpose form panel and offers substantial and surprising resistance to deflection upon loading by providing a double hat section as a cross stiffener member and with side rail connector areas coincident with the double hat section ribs. Side rail stiffener strips are fastened to the side rails on alternate surfaces of the side rails for added rigidity. Further, provision is made for wall ties to extend through the face of the form and thereby connect parallel, spaced form panels together at locations in addition to normal wall tie placement areas at the side rails. Particular fastening means for either pins connecting panels together orthogonally or wall ties connecting panels together in parallel relationship are disclosed and which are designed to effectively distribute the localized stress occurring in the connection area to the cross stiffener members and thereby more effectively distribute areas of stress throughout the entire form than was previously done. The effect of such a structure is to provide a multipurpose form panel which is substantially more resistant to deflection than prior form panels and which can be used for the three main areas of form use without particular adaption to each use.
All of these features are possible in a form panel which is of greater rigidity that the previous form panels manufactured under the '155 patent and, yet, may be lighter in weight. Specifically, the face sheet may be reduced in thickness, yet the form provides greater resistance to deflection.